Harms does not sell the bubble assembly. He has some really good info posted here about the bubbles though. Just do a search on shakers.
I recently bought a complete shaker from Six Pack Performance. It is really a nice package.
They assemble the entire bubble assembly before shipping and ship it that way. Helps to ensure everything fits together nicely. The base plate, trim ring, and air cleaner lid are all powder coated. The bubbles are already painted black and no holes for the call outs. If you want to put them on, you just have drill the holes yourself.